Engine downsizing is potentially one of the most effective strategies being explored to improve fuel economy. A main problem of downsizing using a turbocharger is the small range of stable functioning of the turbocharger centrifugal compressor at high boost pressures, and hence the measurement of the performance maps of both compressor and turbine. Automotive manufacturers use mainly numerical simulations for internal combustion engines simulations, hence the need of an accurate extrapolation model to get a complete turbine performance map. These complete maps are then used for internal combustion engines calibration. Automotive manufacturers use commercial softwares to extrapolate the turbine narrow performance maps, both mass flow characteristics and the efficiency curve. These extrapolation and simulation softwares are used in the architecture of designing new engines, integrating an ECU calculator as an observer / estimator (in this case estimating the turbocharger speed), validation (MIL) and verification (HIL) of engine control, and also for engine calibration. So an extrapolation model of the performance maps given by the manufacturer should be reliable and accurate. This paper presents an experimental study on a turbocharger turbine with different techniques to measure the widest turbine performance map. A Renault 1.5L Diesel engine turbocharger was modified and tested at Ecole Centrale de Nantes as a project in an industrial chair between Renault, LMS-Siemens and Ecole Centrale de Nantes. On the test rig, the experimental program dealt with traditional turbine and compressor performance measurements at different turbine inlet temperatures which widened the measuring area. Another technique was also to introduce air at high pressure at the compressor inlet increasing thereby its power consumption and expanding the measuring area. Air is also blown to the compressor exit to fill the cavities created on the blades back that cause the surge limit. In the same logic, the volute casing of the compressor was removed to minimize its power consumption and get new measured points. These extensions of the turbine performance maps (mass flow rate) of 400% for some rotational speeds can be useful for extrapolation models that can be used by automotive manufacturers. As for the turbine efficiency, there are different definitions for the turbine efficiency. There is the turbine total-to-static isentropic efficiency and the turbine efficiency including the mechanical losses. These two elements were also calculated for this turbocharger.

This paper aims at introducing an original, simulation based, methodology to optimize air charging system of a medium speed engine in order to improve fuel consumption/NO_x trade-off, over a given load profile. A preliminary study is performed on an engine originally equipped with fixed geometry turbocharger (TC) matched at full load. It shows that improving the TC efficiency has a positive impact at matching point but an adverse effect at lower loads. Therefore matching the TC at part load is more promising when the whole engine operating range is considered. However, this requires using a relief system to avoid unacceptable peak firing pressure at full load, and may alter regulated NO_x emission. A new, original methodology is then proposed. Using an advanced existing algorithm, it allows for simultaneous optimization of injection timing, main TC matching and relief system design. The objective is to minimize fuel consumption averaged over several operating points (corresponding to actual load profile). At the same time, NO_x emission, evaluated on regulatory cycle, is kept below a given limit and others reliability constrains are fulfilled. The methodology is assessed with several case studies: – First, various relief systems (blow-off valve, waste gate (WG) and parallel sequential turbocharger (PTC)) are compared on a given load profile – Then, the dimensioning of a TC+WG system is performed for two different load profiles In both cases, the proposed methodology leads to a charging system design customized for a given user profile, which enables a significant fuel consumption reduction.

The objective of this study is to understand how each variable impacts the optimal configuration of a marine diesel engine equipped with an electric hybrid air-charging system that allows energy assistance and recovery. The aim is to minimize CO₂ emissions by reducing fuel consumption. The hybrid system offers flexibility in adjusting parameters from both the engine and air-charging system. It is compared with the baseline engine, which uses a free-floating turbocharger. The results show a significant improvement at low engine loads, where the baseline engine struggles to provide sufficient air. While turbine speed has little influence, compressor power reduces fuel consumption at low loads. However, at mid loads, resizing the turbomachine is necessary for further improvements. At high loads, full optimization of all variables is required to reduce fuel consumption. The electric hybrid system is particularly effective in tugboat-like conditions, where low loads dominate, but less impactful for ro-pax ferries. Despite the potential of the hybrid system, a fully optimized turbocharger could provide greater benefits due to reduced losses. Future studies could explore combining the adaptability of the hybrid system with a highly efficient turbocharger to reduce emissions across all load conditions.

To comply with the evermore stringent polluting emission regulation, such as Euro 6c and its new homologation WTLP cycle, the use of turbochargers, already high in Diesel engines, is steeply rising in Gasoline ones. Turbochargers come into a large variety of implementations such as single/two stage(s) or even parallel. In the meantime, car manufacturers intend to decrease development cost and time by using more and more simulation over experimental measurements. However, usual turbocharger models have not followed this trend of modernity.While the heating part of the standard driving test cycle becomes a major topic, turbocharger models are still map based, built from turbocharger manufacturer’s data and measured only in hot conditions. To improve their accuracy, new turbocharger models need to take into account the thermal transfers. The phenomenon has been widely studied, and different models have been proposed to solve this problem but they require specific data for their calibration. This is hardly compatible with the industry habits.Deriving from an initial turbocharger model with thermal transfer, this paper presents a method to evaluate quasi-adiabatic turbine and compressor maps, using only the standard turbocharger maps and geometrical data and without using any specific testing. Furthermore, to comply with the industry constraints, two calibration levels are proposed, depending on which geometrical data is available. In order to test this method, an implementation in the commercial Simcenter Amesim™ software has been done. Finally, an experimental campaign on 4 different turbochargers of various sizes is conducted to validate the model.